This brings their names to the attention of confidence man James Arnold (Webb), who tries to interest them in a fraudulent scheme to extract treasure from a sunken wreck.

The father declines, but the son accepts, lured by a young woman with the con man, Edna Gordon (Darmond), whom Luther is tricked into marrying.

As a result of the dive to the treasure ship Luther is stricken with the bends, and after he returns home to find that his wife has abandoned him, he becomes desperately ill.

James follows them to rescue his lover, Edna, from her father-in-law, but before they are able to escape her cabin the ferry rams into a derelict hidden by a fog bank, and the ship rapidly begins to sink.

Luther refuses to accept his father's story, and risks his life to make the dive down to the sunken ferry only to discover the floating bodies of his wife and her lover, James.